In recent yeas, development of polymer materials has been drastic and in terms of applications, the polymer materials are used not only for daily necessaries but also range all industrial fields such as automobiles, aircrafts, electronic devices, medical devices, etc. The reason for that may be said that resins with various structures have been developed and have satisfied the needs flexibly. However, the specs required for the polymer materials become further higher and it becomes impossible for an already existing single resin to satisfy an aim. Therefore, development of innovative materials has actively been performed by employing a technique of combining resins having different physical properties and extracting the advantages of the respective resins to be raw materials and compensating for their disadvantages one another, so-called a polymer-alloying technique, to draw excellent characteristics as compared with those of a single resin.
No need to say that the physical properties of raw material resins cause significant effects, the characteristics of a polymer alloy are significantly changed in accordance with dispersion phases and uniformity of these resins and it is expected to improve dynamic characteristics such as toughness by controlling the dispersion phase size to be 1 μm or smaller and evenly (Patent Document 1). Known as a polymer alloy obtained by once causing phase dissolution of two or more kinds of resins in one-phase and thereafter carrying out phase separation are those obtained by nuclei production and growth and those obtained by spinodal decomposition. In polymer alloying by nuclei production and growth, a dispersion structure, which is an island structure, is formed from the beginning and the structure is grown, so that it becomes difficult to control the dispersion phase size to be 1 μm or smaller and even. On the other hand, in spinodal decomposition, when the temperature of the mixture system once subjected to even phase dissolution at a temperature in phase dissolution range is quickly changed to an unstable range, the system swiftly starts phase separation toward a coexistence composition. In that time, the concentration is made monochromic at a constant wavelength and it is made possible to form both-phase continuous structure in which both separated phases are continuously and regularly entwined each other in a structure cycle.
Production methods of a polymer alloy by spinodal decomposition can be broadly divided into those by spinodal decomposition in a partial phase dissolution system and those by induction of spinodal decomposition by melt-kneading in a non-phase dissolution system. The former has problems not only limitation in usable polymers but also difficulty of controlling the dispersion diameter sine the temperature alteration is small. On the other hand, the latter, which is a method of inducing spinodal decomposition by once causing phase dissolution in a shearing condition at the time of melt-kneading and again producing an unstable state in an un-shearing condition, has a problem that the shearing is difficult to be carried out evenly and thus the evenness of the dispersion phase is lowered and also a problem that molecular weights are lowered by shearing.
To deal with such problems, in a polymer alloy of thermosetting resins, there is a method of obtaining a finely and evenly structure-controlled polymer alloy by inducing spinodal decomposition by causing a crosslinking reaction of precursors of the constituent thermosetting resins (Patent Document 2). Since the spinodal curve is changed due to the crosslinking reaction and the unstable region is expanded, this method is capable of controlling the structure more finely as compared with a method by temperature change of a partial phase dissolution system in which the spinodal curve is not changed and since the shearing is no need in the melt-kneading, the method is a method capable of obtaining an even structure. However, because of a polymer alloy of thermosetting resins, it is difficult to employ a molding method such as injection molding and extrusion molding for the obtained polymer alloy.    Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. HEI3-20333    Patent Document 2: JP-A No. 2003-286414